Shock absorber

ABSTRACT

An elastic seal member fixedly attached to a back surface side of a disk valve is fitted in a recessed portion of a pilot body, by which a pilot chamber is formed. A valve opening of the disk valve is controlled by an inner pressure in the pilot chamber. The elastic seal member includes a thick proximal portion and a thin lip portion. A seal portion protruding on an outer circumferential portion of the lip portion is in sliding contact with an inner circumferential portion of an outer cylindrical portion of the pilot body. Deflection of the thin lip portion can reduce sliding resistance while ensuring a sealing performance of the seal portion.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a shock absorber configured to generate a damping force against a stroke of a piston rod.

2. Description of the Related Art

Generally, a tubular hydraulic shock absorber mounted on a suspension apparatus of a vehicle, such as an automobile, is configured in such a manner that a piston with a piston rod coupled thereto is slidably fitted in a cylinder sealingly containing fluid, and a damping force adjustment mechanism including an orifice, a disk valve, and/or the like controls a flow of the fluid that is caused by a sliding displacement of the piston in the cylinder, thereby generating a damping force against a stroke of the piston rod.

Further, a hydraulic shock absorber disclosed in Japanese Patent Public Disclosure No. 2006-38097 includes a backpressure chamber (a pilot chamber) formed behind a disk valve, which is a damping force generation mechanism, with a flow of fluid partially introduced into the backpressure chamber to apply an inner pressure in the backpressure chamber in a direction causing the disk valve to be closed. Then, this hydraulic shock absorber controls valve opening of the disk valve by adjusting the inner pressure in the backpressure chamber.

This configuration can enhance flexibility in adjusting a damping force characteristic.

SUMMARY OF THE INVENTION

In the above-described shock absorber disclosed in Japanese Patent Public Disclosure No. 2006-38097, the backpressure chamber is formed by fixedly attaching a ring-shaped seal member made of an elastic member, such as a rubber, to an outer circumferential portion of a back surface of the disk valve by vulcanization, adhesion, or the like, and slidably and liquid-tightly fitting this seal member to a cylindrical portion of a bottomed cylindrical member disposed behind the disk valve.

The disk valve configured to use the ring-shaped seal member fixedly attached to one side in this manner necessitates a sufficient increase in a pressing force applied to a sliding portion to ensure a sealing performance of the seal member. However, the increase in the pressing force leads to an increase in a sliding resistance accordingly. A set load (a preload) is provided to the disk valve to prevent this sliding resistance from making it difficult to close the disk valve, so as to ensure that the disk valve can be closed by being seated on the seat portion at the time of valve closing.

However, in recent years, the damping force adjustable shock absorber mounted on the suspension apparatus of the vehicle, such as the automobile, has been subject to a demand of sufficiently reducing the damping force in a region where a piston speed is low when the damping force characteristic is switched to a soft side, and providing the set load to the disk valve works against this demand.

The present invention has been contrived in consideration under these circumstances, and an object thereof is to provide a shock absorber that can reduce a sliding resistance while ensuring a sealing performance of an elastic seal member fixedly attached to a disk valve to form a pilot chamber.

To achieve the above-described object, according to an aspect of the present invention, a shock absorber includes a cylinder sealingly containing hydraulic fluid, a piston slidably inserted in the cylinder, a piston rod coupled with the piston and extending out of the cylinder, a disk valve configured to, with respect to a flow of the hydraulic fluid that is caused by a sliding displacement of the piston, generate a damping force by being separated from or seated onto a valve seat to control the flow, a bottomed cylindrical pilot body opened toward the disk valve, and an annular elastic seal member fixedly attached to an outer circumferential portion of one surface side of the disk valve and slidably and liquid-tightly fitted to an inner circumferential portion of the pilot body. The elastic seal member forms a pilot chamber configured to apply an inner pressure therein to the disk valve in a valve-closing direction. The elastic seal member includes an annular proximal portion fixedly attached to the disk valve, an annular lip portion extending from the proximal portion toward a bottom portion of the pilot body, having a radially thinner thickness than the proximal portion, and forming a stepped portion on an inner circumferential side between the proximal portion and the lip portion, and an annular seal portion protruding an outer circumferential portion of the lip portion and slidably contacting the inner circumferential portion of the pilot body.

According to the above-described configuration, it is possible to reduce the sliding resistance while ensuring the sealing performance of the elastic seal member fixedly attached to the disk valve to form the pilot chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a damping force adjustable shock absorber according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of a damping force generation mechanism of the damping force adjustable shock absorber illustrated in FIG. 1.

FIG. 3 illustrates a hydraulic circuit of the damping force adjustable shock absorber illustrated in FIG. 1.

FIG. 4 is an enlarged vertical cross-sectional view of a disk valve portion of the damping force generation mechanism illustrated in FIG. 2.

FIG. 5 is a vertical cross-sectional view of an elastic seal member portion of the disk valve illustrated in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, one embodiment of the present invention will be described in detail with reference to the drawings.

As illustrated in FIG. 1, a damping force adjustable shock absorber 1 according to the present embodiment has a twin-tube structure including an outer tube 3 disposed outside a cylinder 2, with a reservoir 4 formed between the cylinder 2 and the outer tube 3. A piston 5 is slidably fitted in the cylinder 2, and this piston 5 divides the inside of the cylinder 2 into two chambers, a cylinder upper chamber 2A and a cylinder lower chamber 2B. One end of a piston rod 6 is coupled to the piston 5 by a nut 7. An opposite end side of the piston rod 6 penetrates through the cylinder upper chamber 2A, is inserted through a rod guide 8 and an oil seal 9 attached to upper ends of the cylinder 2 and the outer tube 3, and extends out of the cylinder 2. A base valve 10 is provided at a lower end of the cylinder 2. The base valve 10 separates the cylinder lower chamber 2B and the reservoir 4 from each other.

Passages 11 and 12 are provided through the piston 5. The passages 11 and 12 establish communication between the cylinder upper and lower chambers 2A and 2B. Then, a check valve 13 is provided in the passage 12. The check valve 13 permits fluid only to flow from the cylinder lower chamber 2B side to the cylinder upper chamber 2A side, and is provided a set load sufficiently small to allow the check valve 13 to be opened at the moment that the piston rod 6 is switched from an extension stroke to a compression stroke. Further, a disk valve 14 is provided in the passage 11. The disk valve 14 is opened when a pressure of the fluid on the cylinder upper chamber 2A side reaches a predetermined pressure during the extension stroke, and releases this pressure to the cylinder lower chamber 2B side. A valve-opening pressure of this disk valve 14 is considerably high, and is set to a valve-opening pressure that prohibits the disk valve 14 to be opened while a vehicle is running on a normal road surface, and an orifice 14A (refer to FIG. 3), which establishes a constant connection between the cylinder upper and lower chambers 2A and 2B, is provided at the disk valve 14.

Passages 15 and 16 are provided through the base valve 10. The passages 15 and 16 establish communication between the cylinder lower chamber 2B and the reservoir 4. Then, a check valve 17 is provided in the passage 15. The check valve 17 permits the fluid only to flow from the reservoir 4 side to the cylinder lower chamber 2B side, and is provided a set load sufficiently small to allow the check valve 17 to be opened at the moment that the piston rod 6 is switched from the compression stroke to the extension stroke. Further, a disk valve 18 is provided in the passage 16. The disk valve 18 is opened when a pressure of the fluid on the cylinder lower chamber 2B side reaches a predetermined pressure, and releases this pressure to the reservoir 4 side. A valve-opening pressure of this disk valve 18 is considerably high, and is set to a valve-opening pressure that prohibits the disk valve 18 to be opened while the vehicle is running on the normal road surface, and an orifice 18A (refer to FIG. 3), which establishes a constant connection between the cylinder lower chamber 2B and the reservoir 4, is provided at the disk valve 18. Oil is sealingly contained in the cylinder 2, and oil and gas are sealingly contained in the reservoir 4, as hydraulic fluid.

A separator tube 20 is externally fitted to the cylinder 2 at both the upper and lower ends thereof via seal members 19, with an annular passage 21 formed between the cylinder 2 and the separator tube 20. The annular passage 21 is in communication with the cylinder upper chamber 2A via a passage 22 formed through a sidewall of the cylinder 2 in the vicinity of the upper end thereof. A plurality of passages 22 may be provided while being arranged circumferentially, depending on a specification. A cylindrical connection port 23 is formed at a lower portion of the separator tube 20. The connection port 23 protrudes and is opened laterally. Further, an opening 24 is formed through a sidewall of the outer tube 3. The opening 24 is concentric with the connection port 23, and is larger in diameter than the connection port 23. A cylindrical case 25 is coupled to the sidewall of the outer tube 3 by welding or the like so as to surround this opening 24. Then, a damping force generation mechanism 26 is attached in the case 25.

Next, the damping force generation mechanism 26 will be described with reference to mainly FIGS. 2 and 3. The damping force generation mechanism 26 includes a main valve 27, a control valve 28, and a pilot valve 29. The main valve 27 and the control valve 28 are a pilot-type valve mechanism, and the pilot valve 29 is a pressure control valve configured to be driven by a solenoid.

The main valve 27 includes a disk valve 30 and a pilot chamber 31. The disk valve 30 is opened by receiving the pressure of the fluid on the cylinder upper chamber 2A side, thereby permitting this fluid to flow toward the side of the reservoir 4. The pilot chamber 31 applies an inner pressure therein to this disk valve 30 in a valve-closing direction. The pilot chamber 31 is connected to the side of the cylinder upper chamber 2A via a fixed orifice 32, and is also connected to the side of the reservoir 4 via the control valve 28. An orifice 30A is provided at the disk valve 30. The orifice 30A establishes a constant connection between the side of the cylinder upper chamber 2A and the side of the reservoir 4.

The control valve 28 includes a disk valve 33 and a pilot chamber 34. The disk valve 33 is opened by receiving a pressure of the fluid on the side of the pilot chamber 31, thereby permitting this fluid to flow toward the side of the reservoir 4. The pilot chamber 34 applies an inner pressure therein to this disk valve 33 in a valve-closing direction. The pilot chamber 34 is connected to the side of the cylinder upper chamber 2A via a fixed orifice 35, and is also connected to the side of the reservoir 4 via the pilot valve 29. An orifice 33A is provided at the disk valve 33. The orifice 33A establishes a constant connection between the side of the pilot chamber 31 and the side of the reservoir 4.

The pilot valve 29 is configured to narrow a flow passage with a small-diameter port 36, and adjust the inner pressure in the pilot chamber 34 of the control valve 28 by opening and closing this port 36 by a valve body 38 driven by a solenoid 37. The small diameter of the port 36 leads to a small pressure-receiving area, which allows the pilot valve 29 to achieve a high pressure when being closed under a maximum electric current. This configuration results in an increase in a differential pressure between a high electric current and a low electric current, thereby succeeding in expanding a range where the damping force characteristic can vary.

Next, a specific configuration of the damping force generation mechanism 26 will be described in further detail with reference to mainly FIG. 2.

A main body 39, a control body 40, and a pilot body 41 with the main valve 27, the control valve 28, and the pilot valve 29 installed therein are disposed in the case 25 together with a passage member 42, and a solenoid case 43 is attached to an end of an opening of the case 25 by a nut 44 to sealingly close the case 25, by which these components are fixed to the case 25. The solenoid case 43 has a generally cylindrical shape containing an intermediate wall 43A axially dividing the inside of the solenoid case 43. One end of the solenoid case 43 is inserted and fitted in the case 25. Further, an opposite end of the solenoid case 43 is fixed to the case 25 by the nut 44 while protruding out of the case 25. An opening 43B and an annular recessed portion 43C are formed through and at the intermediate wall 43A. The opening 43B penetrates through a center of the intermediate wall 43A. The annular recessed portion 43C is formed around a one-end side of the opening 43B.

The passage member 42 has a cylindrical shape including a flange portion 42A on an outer circumference at one end thereof. The flange portion 42A is in abutment with an inner flange portion 25A of the case 25, and a cylindrical portion of the passage member 42 is liquid-tightly inserted in the connection port 23 of the separator tube 20, by which the passage member 42 is connected to the annular passage 21. A plurality of radially extending passage grooves 25B is formed on the inner flange portion 25A of the case 25. The reservoir 4 and a chamber 25C in the case 25 are in communication with each other via these passage grooves 25B and the opening 24 of the outer tube 3.

The main body 39 and the control body 40 each have an annular shape, and the pilot body 41 has a stepped cylindrical shape including a large-diameter portion 41A at an intermediate portion thereof. A cylindrical portion 41B on an one-end side of the pilot body 41 is inserted in the main body 39 and the control body 40, and a cylindrical portion 41C on an opposite-end side the pilot body 41 is fitted in the recessed portion 43C of the intermediate wall 43A of the solenoid case 43, by which these components are positionally fixed concentrically with one another.

A plurality of axially penetrating passages 39A is formed through the main body 39 while being arranged along a circumferential direction. The passages 39A are in communication with the passage member 42 via an annular recessed portion 45 formed at one end of the main body 39. An annular seat portion 46 and an annular clamp portion 47 protrude on an outer circumferential side and an inner circumferential side of openings of the plurality of passages 39A on an opposite end of the main body 39, respectively. An outer circumferential portion of the disk valve 30, which constitutes the main valve 27, is seated on the seat portion 46 of the main body 39. An inner circumferential portion of the disk valve 31 is clamped between the clamp portion 47 and the control body 40 together with an annular retainer 48 and a washer 49. An annular elastic seal member 50 made of an elastic member, such as a rubber, is fixedly attached to an outer circumferential portion on a back surface side of the disk valve 30 by a fixing attachment method, such as vulcanization adhesion. The disk valve 30 is formed by stacking flexible disk-shaped valve bodies as necessary so as to acquire a desired deflection characteristic. Further, a cutout is formed on the outer circumferential portion of the disk valve 30. This cutout forms the orifice 30A, which establishes constant communication between the passage 39A side and the reservoir chamber 25C side.

An annular recessed portion 51 is formed on a one-end side of the control body 40. An outer circumferential portion of the elastic seal member 50 fixedly attached to the disk valve 30 is slidably and liquid-tightly fitted in this recessed portion 51, by which the pilot chamber 31 is formed within the recessed portion 51. The disk valve 30 is lifted from the seat portion 46 to be opened by receiving a pressure on the passage 39 A side, thereby establishing the communication between the passages 39A and the chamber 25C in the case 25. The inner pressure in the pilot chamber 31 is applied to the disk valve 30 in the valve-closing direction. The pilot chamber 31 is in communication with the inside of the cylindrical portion 41B via a fixed orifice 32 formed through a sidewall of the retainer 48 and a passage 52 formed through a sidewall of the cylindrical portion 41B of the pilot body 41, and is further in communication with the passage member 42. Further, a bottom portion forming the annular recessed portion 51 of the control body 40 is formed so as to have a thickness increasing toward a central side, i.e., the pilot body 41 side. The reason therefor is as follows. The central side, i.e., the pilot body 41 side is subject to application of an axial force and therefore should be rigid, whereby the bottom portion is formed sufficiently thickly here. On the other hand, the bottom portion is formed thinly on an outer circumferential side thereof compared to the central side to allow the pilot chamber 31 to have a sufficient volume.

A plurality of axially penetrating passages 53 is formed through the control body 40 while being arranged along a circumferential direction. One ends of the passages 53 are in communication with the pilot chamber 31. An annular inner seat portion 54 is protrudingly provided as a valve seat on an outer circumferential side of openings of the plurality of passages 53 on an opposite end of the control body 40. An outer seat portion 55 is protrudingly provided on an outer circumferential side of the inner seat portion 54. Further, an annular clamp portion 56 is protrudingly provided on an inner circumferential side of the plurality of passages 53. The disk valve 33, which constitutes the control valve 28, is seated on the inner and outer seat portions 54 and 55. An inner circumferential portion of the disk valve 33 is clamped between the clamp portion 56 and the large-diameter portion 41 a of the pilot body 41 together with a washer 57. An annular elastic seal member 58 made of an elastic member, such as a rubber, is fixedly attached to an outer circumferential portion on a back surface side of the disk valve 33 by a fixing attachment method, such as the vulcanization adhesion. The disk valve 33 is formed by stacking flexible disk-shaped valve bodies as necessary so as to acquire a desired deflection characteristic. The disk valve 33 will be described in further detail below.

The annular recessed portion 59 is formed on a one-end side of the large-diameter portion 41A of the pilot body 41. The annular recessed portion 59 serves as a pilot case forming the pilot chamber 34. An outer circumferential portion of the elastic seal member 58 fixedly attached to the disk valve 33 is slidably and liquid-tightly fitted in this recessed portion 59, by which the pilot chamber 34 is formed in the recessed portion 59. The disk valve 33 is sequentially lifted from the outer and inner seat portions 55 and 54 to be opened by receiving a pressure on the passage 53 side in communication with the pilot chamber 31 of the main valve 27, thereby establishing communication between the passages 53 and the chamber 25C in the case 25. The inner pressure in the pilot chamber 34 is applied to the disk valve 33 in the valve-closing direction. The pilot chamber 34 is in communication with a passage 41D in the cylindrical portion 41B via a passage 60 formed through a sidewall of the pilot body 41, and is further in communication with the inside of the passage member 42 via a fixed orifice 35 and a filter 61 provided in the cylindrical portion 41B. The fixed orifice 35 and the filter 61 are fixed to a stepped portion 64 in the cylindrical portion 41B by a cylindrical retainer 62 threadably inserted in a distal portion of the cylindrical portion 41B, and a spacer 63. A cutout 63A is formed through a sidewall of the spacer 63. The cutout 63A establishes communication between the fixed orifice 35 and the passage 41D in the cylindrical portion 41B.

A guide member 65 is inserted in the cylindrical portion 41C on the opposite end of the pilot body 41, the opening 43B of the solenoid case 43, and the recessed portion 43C of the solenoid case 43. The guide member 65 has a stepped cylindrical shape including a small-diameter port press-fitting portion 65A on a one-end side thereof, a small-diameter plunger guide portion 65B on an opposite-end side thereof, and a large-diameter portion 65C at an intermediate portion thereof. The guide member 65 is fixed by the port press-fitting portion 65A inserted in the cylindrical portion 41C of the pilot body 41 with a space formed therebetween, the plunger guide portion 65B inserted through the opening 43B of the solenoid case 43 to protrude into the opposite-end side of the solenoid case 43, and the large-diameter portion 65C fitted in the recessed portion 43C of the solenoid case 43 while being in abutment with the cylindrical portion 41C of the pilot body 41 that is inserted and fitted in the recessed portion 43C.

A generally cylindrical port member 67 is press-fitted and fixed in the port press-fitting portion 65A of the guide member 65. An annular retainer 66 is attached to a distal portion of the port press-fitting portion 65A. An O-ring 70 seals between an outer circumferential surface of the port member 65 and an inner circumferential surface of the cylindrical portion 41C of the pilot body 41. A passage 68 in the port member 67 is in communication with the passage 41D in the pilot member 41.

The port 36 is formed at an end of the port member 67 that is press-fitted in the guide member 65. The port 36 is formed by reducing an inner diameter of the passage 68. The port 36 is opened to the inside of a valve chamber 73 formed in the guide member 65. The valve chamber 73 is in communication with the chamber 25C in the case 25 via an axial groove 74 formed on the port press-fitting portion 65A of the guide member 65, an annular recessed portion 69 formed at an inner circumferential edge of an opening of the port press-fitting portion 65A, a radial passage 75 formed through the retainer 66, an annular space 76 between the port press-fitting portion 65A of the guide member 65 and the cylindrical portion 41C of the pilot body 41, and a passage 77 penetrating through the sidewall of the cylindrical portion 41C. The passage 68 in the port member 67 is in communication with the pilot chamber 34 via the passage 60, and is in communication with the inside of the passage member 42 via the fixed orifice 35 and the filter 61.

A plunger 78 is inserted in the plunger guide portion 65B of the guide member 65, and is slidably guided in the plunger guide portion 65B along an axial direction. The tapering valve body 38 is provided at a distal portion of the plunger 78. The valve body 38 is inserted in the valve chamber 73 in the guide member 65, and opens and closes the port 36 by being separated from and seated on a seat portion 36A at an end of the port member 67. A large-diameter armature 79 is provided at a proximal portion of the plunger 78. The armature 79 is disposed outside the plunger guide 65B. A generally bottomed cylindrical cover 80 covering the armature 79 is attached to the plunger guide portion 65B. The cover 80 guides the armature 79 movably along the axial direction.

The solenoid 37 is disposed around the plunger guide portion 65B protruding from the intermediate wall 43A of the solenoid case 43 and the cover 80 in the solenoid case 43. The solenoid 37 is fixed by a closing member 81 attached to the opening of the solenoid case 43. A lead wire (not illustrated) connected to the solenoid 37 extends to the outside via a cutout 81A of the closing member 81. The plunger 78 is urged in a valve-opening direction for separating the valve body 38 from the seat portion 36A to open the port 36 by a spring force of a return spring 84 disposed between the plunger 78 and the port member 67. Power supply to the solenoid 37 generates a thrust force, thereby causing the plunger 78 to be displaced in a valve-closing direction for seating the valve boy 38 onto the seat portion 36A to close the port 36 against the spring force of the return spring 84.

Next, the disk valve 33 of the control valve 28 will be described in further detail with reference to FIGS. 4 and 5.

As illustrated in FIG. 4, the disk valve 33 includes the elastic seal member 58 made of the elastic member, such as the rubber, fixedly attached to an outer circumferential portion of a one-surface side, i.e., the back surface-side (the pilot chamber 34 side) of the metallic disk main body 90. In the present embodiment, the elastic seal member 58 is made of the rubber, and is fixedly attached to the disk main body 90 by the vulcanization adhesion, but another method may be employed as the fixing attachment method. A disk-shaped spacer 91 and a seat disk 92 are stacked on an opposite-surface side, i.e., a front-surface side (the inner and outer seat portion 54 and 55 side) of the disk valve 33.

The elastic seal member 58 has such a generally trapezoidal shape in cross-section that an outer circumferential side and an inner circumferential side thereof are inclined radially inwardly and outwardly, respectively, and an inner circumferential portion of a distal end of the trapezoid is cutout. Further, this cross-sectional shape forms a stepped shape including a radially thick proximal portion 58A, a radially thinner lip portion 58B than the proximal portion 58A, and a stepped portion 58C therebetween. Inner circumferential portions of the proximal portion 58A and the lip portion 58B are inclined in such a manner that diameters thereof are increasing toward a bottom portion of the recessed portion 59 of the pilot body 41. The inner circumferential sides of the proximal portion 58A and the lip portion 58B are inclined at approximately equal angles to each other, but larger angles than angles at which outer circumferential sides thereof are inclined. The stepped portion 58C between the proximal portion 58A and the lip portion 58B extends generally in parallel with the disk main body 90. A flange portion 58D protrudes radially outwardly at a portion of the proximal portion 58A where the proximal portion 58A is coupled with the disk main body 90.

Further, as illustrated in FIG. 5, a seal portion 58E generally triangular in cross-section protrudes radially outwardly at an axial center of the outer circumferential portion of the lip portion 58B of the elastic seal member 58. The seal portion 58E is in sliding contact with an inner circumferential surface of an outer cylindrical portion 41E forming the recessed portion 59 of the pilot body 41. A plurality of seal protrusions 58F (in the illustrated example, two seal protrusions 58F) generally semi-circular in cross-section protrudes at an inclined portion of the seal portion 58E on a proximal portion 58A side while being arranged along the inclination. As illustrated in FIG. 4, when the elastic seal member 58 is fitted in the recessed portion 59 of the pilot body 41, the lip portion 58B is deflected toward the inner circumferential side around the stepped portion 58C serving as a supporting point, and the seal portion 58E is deformed by being pressed against an inner circumferential cylindrical surface 59A of the recessed portion 59 into close contact with the inner circumferential cylindrical surface 59A of the recessed portion 59. In other words, when the elastic seal member 58 is attached in the pilot body 41, the elastic seal member 58 is deformed from the shape thereof before being attached in the pilot body 41 in such a manner that the lip portion 58B is bent toward the inner circumferential cylindrical surface 59A on a radially inner side of the pilot body 41 around the stepped portion 58C serving as the supporting point, where the inner circumference of the lip portion 58B is connected to the proximal portion 58A. In this state, a space is generated between the lip portion 58B except for the seal portions 58E and the inner circumferential cylindrical surface 59A of the recessed portion 59.

As illustrated in FIG. 4, when the disk valve 33 is seated on the inner seat portion 54 and the outer seat portion 55, a distance L1 between the stepped portion 58C of the elastic seal member 58 and the disk main body 90 is longer than a distance L2 between a distal portion of the outer cylindrical portion 41E of the pilot body 41 that forms the recessed portion 59 which the elastic seal member 58 is in abutment with, and the disk main body 90.

Orifice holes 92A and 92B are provided at the seat disk 92 at positions facing the inner and outer seat portions 54 and 55, respectively. An orifice 33A, which establishes constant communication between the pilot chamber 31 and the chamber 25C, is formed by the orifice holes 92A and 92B. An outer diameter of the disk main body 90 of the disk valve 33 is larger than an inner diameter of the outer cylindrical portion 41E of the pilot body 40. The outer circumferential portion of the disk main body 90 and the distal portion of the outer cylindrical portion 41E face each other with the space L2 generated therebetween.

The disk valve 33, the spacer 91, and the seat disk 92 each have a flat-plate shape. The clamp portion 56, the inner seat portion 54, and the outer seat portion 55 of the control body 40 protrude by approximately equal lengths to one another. This configuration allows the disk valve 33 (the seat disk 29, the spacer 91, and the disk main body 90) to be seated on the inner seat portion 54 and the outer seat portion 55 with a sufficiently small (almost zero) seat load (preload) provided thereto, i.e., without being deflected.

In the present embodiment, the elastic seal member 50 of the disk valve 30 of the main valve 27 is configured similarly to the above-described elastic seal member 58 of the disk valve 33 of the control valve 28, but may be configured in a conventional manner.

An operation of the damping force adjustable shock absorber 1 configured in this manner will be described next. The damping force adjustable shock absorber 1 is mounted between a sprung side and an unsprung side of a suspension apparatus of the vehicle. When being in a normal operation state, the damping force adjustable shock absorber 1 performs pressure control with use of the pilot valve 29 by supplying power to the solenoid 37, generating a thrust force on the plunger 78, and seating the valve body 38 onto the seat portion 36A according to an instruction from an in-vehicle controller or the like.

During the extension stroke of the piston rod 6, a displacement of the piston 5 in the cylinder 2 causes the check valve 13 of the piston 5 to be kept closed, and thus the fluid on the cylinder upper chamber 2A side, which corresponds to an upstream chamber, to be pressurized to be then delivered through the passage 22 and the annular passage 21 to be introduced into the passage member 42 of the damping force generation mechanism 26 via the connection port 23 of the separator tube 20, before the disk valve 14 is opened.

At this time, the oil is supplied by an amount corresponding to the displacement of the piston 5 from the reservoir 4 into the cylinder lower chamber 2B by opening the check valve 17 of the base valve 10. When the pressure in the cylinder upper chamber 2A reaches the valve-opening pressure of the disk valve 14 of the piston 5, the disk valve 14 is opened to release the pressure in the cylinder upper chamber 2A to the cylinder lower chamber 2B, which prevents the pressure in the cylinder upper chamber 2A from excessively increasing.

During the compression stroke of the piston rod 6, a displacement of the piston 5 in the cylinder 2 causes the check valve 13 at the piston 5 to be opened and the check valve 17 in the passage 15 of the base valve 10 to be kept closed. Then, before the disk valve 18 is opened, the fluid in the piston lower chamber 2B is introduced into the cylinder upper chamber 2A, and the fluid is transmitted by an amount corresponding to an entry of the piston rod 6 into the cylinder 2 from the cylinder upper chamber 2A, which corresponds to the upstream chamber, into the reservoir 4 by passing through a similar route to the flow during the above-described extension stroke. When the pressure in the cylinder lower chamber 2B reaches the valve-opening pressure of the disk valve 18 of the base valve 10, the disk valve 18 is opened to release the pressure in the cylinder lower chamber 2B into the reservoir 4, which prevents the pressure in the cylinder lower chamber 2B from excessively increasing.

At the damping force generation mechanism 26, the oil conveyed from the passage member 42 is introduced into the reservoir 4, which corresponds to a downstream chamber, by passing through mainly the following three flow passages.

(1) Main Flow Passage

The oil conveyed from the passage member 42 is transmitted through the passages 39A of the main body 39, is delivered into the chamber 25C in the case 25 by opening the disk valve 30 of the main valve 27, and is then introduced into the reservoir 4 by passing through the passage grooves 25B and the opening 24.

(2) Control Flow Passage

The oil conveyed into the passage member 42 is transmitted into the pilot chamber 31 by passing through the insides of the retainer 62 and the spacer 63 provided in the cylindrical portion 41 of the pilot body 41, the cutout 63A of the spacer 63, the passage 52 through the sidewall of the cylindrical portion 41B, and the fixed orifice 32. Further, the oil is delivered from the pilot chamber 31 into the chamber 25C in the case 25 by passing through the passages 53 of the control body 40 and opening the disk valve 33 of the control valve 28, and is then introduced into the reservoir 4 by passing through the passage grooves 25B and the opening 24.

(3) Pilot Flow Passage

The oil conveyed into the passage member 42 is transmitted through the insides of the retainer 62 and the spacer 63, the filter 61, the fixed orifice 35, and the passage 41D provided in the cylindrical portion 41B of the pilot body 41. Further, the oil is delivered into the valve chamber 73 by passing through the passage 68 and the port 36 of the port member 67, and opening the valve body 38 of the pilot valve 29. Then, the oil is forwarded into the chamber 25C in the case 25 by passing through the axial groove 74, the annular recessed portion 69, the radial passage 75, the space 76, and the passage 77, and is then introduced into the reservoir 4 by flowing through the passage grooves 25B and the opening 24.

As a result, the damping force is generated with the aid of the main valve 27, the control valve 28, and the pilot valve 29 of the damping force generation mechanism 26 during both the extension stroke and the compression stroke of the piston rod 6. At this time, the disk valve 30 of the main valve 27 is opened by receiving the pressure on the passage 39A side, while the inner pressure in the pilot chamber 31 provided on the back surface side is applied in the valve-closing direction. In other words, the disk valve 30 is opened based on the differential pressure between the passage 39A side and the pilot chamber 31 side, whereby a reduction in the inner pressure leads to a reduction in the valve-opening pressure, and an increase in the inner pressure leads to an increase in the valve-opening pressure according to the inner pressure in the pilot chamber 31.

Further, the disk valve 33 of the control valve 28 is opened by receiving the pressure on the passage 53 side, while the inner pressure in the pilot chamber 34 formed on the back surface side is applied in the valve-closing direction. In other words, the disk valve 33 is opened based on the differential pressure between the passage 53 side and the pilot chamber 34 side, whereby a reduction in the inner pressure leads to a reduction in the valve-opening pressure, and an increase in the inner pressure leads to an increase in the valve-opening pressure according to the inner pressure in the pilot chamber 34.

When the piston speed falls in a low speed region, the main valve 27 and the control valve 28 are kept closed, and the oil is introduced into the reservoir 4 by passing through mainly the above-described pilot flow passage (3), and the orifice holes 92A and 92B (the orifice 33A) provided at the disk valve 33 of the control valve 28, so that the damping force is generated with the aid of the pilot valve 29 and the orifice 33A. Then, as the pilot speed increases, the pressure on the upstream side of the pilot valve 29 increases. At this time, the inner pressures in the pilot chambers 31 and 34 on the upstream side of the pilot valve 29 are controlled by the pilot valve 29, and reduce when the pilot valve 29 is opened. As a result, first, the disk valve 33 of the control valve 28 is opened, so that the oil is introduced into the reservoir 4 by passing through the control flow passage (2) in addition to the above-described pilot flow passage (3), which can ease an increase in the damping force according to an increase in the piston speed.

When the disk valve 33 of the control valve 28 is opened, the inner pressure in the pilot chamber 31 reduces. The reduction in the inner pressure in the pilot chamber 31 causes the disk valve 30 of the main valve 27 to be opened, and thus the oil to be introduced into the reservoir 4 by passing through the main flow passage (1) in addition to the above-described pilot flow passage (3) and control flow passage (2), which can ease the increase in the damping force according to the increase in the piston speed.

In this manner, an appropriate damping force characteristic can be acquired by easing the increase in the damping force according to the increase in the piston speed in two steps. Then, the inner pressure in the pilot chamber 34 of the control valve 28, i.e., the valve-opening pressure of the disk valve 33 can be controlled by adjusting the pressure for controlling the pilot valve 29 based on the power supply to the solenoid 37. Further, the inner pressure in the pilot chamber 31 of the main valve 27, i.e., the valve-opening pressure of the disk valve 30 can be controlled based on the valve-opening pressure of the disk valve 33.

Due to this configuration, the disk valve 33 of the control valve 28 in addition to the pilot valve 29 is opened in a region where the main valve 27 is closed, so that a sufficient flow amount of the oil can be acquired, which allows the pilot valve 29 to have a small flow amount (a flow passage area of the port 36), and thus the pilot valve 29 (a solenoid valve) to reduce in size and the solenoid 37 to consume lower power. Further, the damping force can be changed in two steps with the aid of the main valve 27 and the control valve 28, which can enhance the flexibility of adjusting the damping force characteristic to acquire the appropriate damping force characteristic.

At this time, the disk valve 33 of the control valve 28 is provided with the sufficiently small set load (preload), and the valve-opening pressure thereof is set to a low pressure due to a reduction in a sliding resistance compared to the conventional configuration, whereby the valve can be opened in the region where the piston speed is extremely low, and the small damping force can be stably generated when the damping force is rising.

The elastic seal member 58 of the disk valve 33 of the control valve 28 is configured in such a manner that the lip portion 58B has the thinner radial thickness than the proximal portion 58A, and thus becomes easily deflectable radially inwardly around the stepped portion 58C serving the supporting point, which allows the lip portion 58B to be pressed against the inner circumferential cylindrical surface 59A with an appropriately weakened pressing force, thereby reducing in the sliding resistance. This results in a reduction in difficulty for the disk valve 33 to return to the inner and outer seat portions 54 and 55 after being opened, and a reduction in the deflection of the disk valve 33, which are caused by the sliding resistance. Accordingly, this configuration can ensure the close contact between the disk valve 33 (the seat disk 92) and the inner and outer seal portions 54 and 55, thereby succeeding in acquiring the stable damping force characteristic even in the region where the piston speed is extremely low, even when the disk valve 33 is provided with the small set load or no set load. Then, the vale-opening pressure of the disk valve 33 can be set to the sufficiently low pressure, which allows a smaller damping force to be set when the damping force characteristic is on the soft side. The lip portion 58B is pressed against the inner circumferential surface of the outer cylindrical portion 41E by the inner pressure in the pilot chamber 34, and thus can ensure a sealing performance even when the inner pressure in the pilot chamber 34 increases.

Especially, in the case where the valve opening of the pilot-type main valve 27 is controlled by the pilot-type control valve 28, like the present embodiment, the valve-opening pressure of the control valve 28 is set to the low pressure, which allows the damping force to smoothly rise in the region where the piston speed is extremely low, and realizes an ideal damping force characteristic for the suspension apparatus of the vehicle.

Further, the seal portion 58E holds the oil between the plurality of seal protrusions 58F, thereby contributing to reducing the sliding resistance while improving the sealing performance.

The elastic seal member 58 is configured in such a manner that the proximal portion 58A has the radially thicker thickness than the lip portion 58B, thereby contributing to enhancing a pressure tightness against the high pressure in the pilot chamber 34, and preventing the elastic seal member 58 from being detached off from the disk main body 90. An outer circumferential recessed portion 58G is provided between the flange portion 58D at the outer circumferential portion of the proximal portion 58A, and the seal portion 58E, which can prevent the elastic seal member 58 from being displaced outwardly beyond the outer cylindrical portion 41E of the pilot body 41 even when the pressure in the pilot chamber 34 increases to a considerably high pressure.

The present invention can be also applied to a shock absorber including the damping force adjustment mechanism disposed at the piston portion, in addition to the shock absorber including the damping force adjustment mechanism disposed at the side of the cylinder, like the above-described embodiment. Further, the above-described embodiment has been described based on the damping force adjustable shock absorber. However, the present invention is not limited thereto, and can be similarly applied even to a shock absorber that does not adjust the damping force, as long as this shock absorber includes the pilot-type damping valve using the disk valve with the elastic seal member fixedly attached thereto.

Although only some exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

The present application claims priority to Japanese Patent Applications No. 2014-175673 filed on Aug. 29, 2014. The entire disclosure of No. 2014-175673 filed on Aug. 29, 2014 including specification, claims, drawings and summary are incorporated herein by reference in its entirety. 

What is claimed is:
 1. A shock absorber comprising: a cylinder sealingly containing hydraulic fluid; a piston slidably inserted in the cylinder; a piston rod coupled with the piston and extending out of the cylinder; a disk valve configured to, with respect to a flow of the hydraulic fluid that is caused by a sliding displacement of the piston, generate a damping force by being separated from or seated onto a valve seat to control the flow; a bottomed cylindrical pilot body opened toward the disk valve; and an annular elastic seal member fixedly attached to an outer circumferential portion of one surface side of the disk valve and slidably and liquid-tightly fitted to an inner circumferential portion of the pilot body, the elastic seal member forming a pilot chamber configured to apply an inner pressure therein to the disk valve in a valve-closing direction, wherein the elastic seal member includes an annular proximal portion fixedly attached to the disk valve, an annular lip portion extending from the proximal portion toward a bottom portion of the pilot body, having a radially thinner thickness than the proximal portion, and forming a stepped portion on an inner circumferential side between the proximal portion and the lip portion, and an annular seal portion protruding from an outer circumferential portion of the lip portion and slidably contacting the inner circumferential portion of the pilot body, and wherein the stepped portion is disposed at a position closer to the disk valve than a portion of the annular seal portion having a maximum radius in an axial direction of the elastic sealing member.
 2. The shock absorber according to claim 1, wherein an outer diameter of the disk valve is larger than an inner diameter of the inner circumferential portion of the pilot body to which the elastic seal member is fitted, and the outer circumferential portion of the disk valve and one end of the pilot body face each other with a space generated therebetween.
 3. The shock absorber according to claim 2, wherein a flange portion extending so as to face the one end of the pilot body is formed at an outer circumferential portion of the elastic seal member that is fixedly attached to the disk valve, and wherein an outer circumferential recessed portion is formed between the flange portion and the seal portion.
 4. The shock absorber according to claim 2, wherein a distance (L1) between the disk valve and the stepped portion is longer than a distance (L2) of the space formed between the disk valve and the one end of the pilot body when the disk valve is seated on the valve seat.
 5. The shock absorber according to claim 1, wherein a distance between the disk valve and the stepped portion is longer than a distance between the disk valve and the one end of the pilot body when the disk valve is seated on the valve seat.
 6. The shock absorber according to claim 1, wherein inner circumferential portions of the proximal portion and the lip portion of the elastic seal member each have a diameter increasing from the disk valve side to the bottom side of the pilot body.
 7. The shock absorber according to claim 6, wherein the stepped portion includes a planar surface extending generally in parallel with the disk valve, and a stepped shape is formed by the stepped portion between the proximal portion and the lip portion of the elastic seal member.
 8. The shock absorber according to claim 6, wherein inner circumferential portions of the proximal portion and the lip portion of the elastic seal portion include inclined surfaces, respectively, and wherein the inclined surface of the proximal portion is positioned so as to be offset from the inclined surface of the lip portion in a radial direction of the elastic seal member by the stepped portion.
 9. The shock absorber according to claim 1, wherein the lip portion is deflected radially inwardly around the stepped portion serving as a supporting point, when the elastic seal member is fitted in the pilot body.
 10. The shock absorber according to claim 1, wherein the stepped portion includes a planar surface extending generally in parallel with the disk valve, and a stepped shape is formed by the stepped portion between the proximal portion and the lip portion of the elastic seal member.
 11. The shock absorber according to claim 1, wherein the seal portion is formed as a cross-section of a generally triangular shape, and wherein an apex of the generally triangular shape serves as the portion of the seal portion having the maximum radius. 